Turbine blade lashing



June 14, 1949. J). D. CONRAD ETAL TURBINE BLADE LASI-IINGl Filed Nov. '1, 194e Fra..

VE RS D NRAD.

WILLIAM H. I LoYD.

ATTORNEY blades.

Patented June 14, 1949 UNITED STATES PATENT OFFICE house Electric Corporation, East Pittsburgh, Pal, a corporation-of Pennsylvania Application' November 1, 1946, Serial No. 707,244

3` Claims.

The invention relates toturbine. Ablade lashing and it hasl for its lvobject-to vprovide forged rblades having integrallashing-r :projections extending from opposite. blade faces so thatwith the blades assembled inra row,` the 'endsfof the projections may be joined: substantially midway between the blades, the. draft .required forfforging they projections valso serving the ,purpose -ofgiving strength to the lashing.

The longer rotating :turbine blades are usually lashedtogetherrto increase-the natural frequency ofpblade vibration andthereby. vavoid vibration difculties: `over the :rangel of :operating speeds; however.11ashing :ordinarily adversely affects the mechanical. or vphysical mfopertiesy of. the blade. Lashing wire openingsjweaken the :blade section; and fasteningl of the'. lashingV to thebla'des `may involve sacrifice in blade :strengthior impairment of physicaljpropertiessthereof, particularly where the blades are ma'deo'falloy steels, such as stainless steel, which may be injured because of heating involved incident tosoldering' or welding. We overcome these. difficulties. by :forging lashing projections integrally with the blades .andby connecting adjoining projection ends approximately midway between the blades but; to enable this to be done; with the inter-blade lashing `spaces. usually encountered, we provide 'projectionsfcharacterized=rby features contributing to making `it possible to forge relatively long projections incident to forging of the blades and which projections, when joined, constitute strong lashing structures connecting adjacent blades.

Turbine blade lashing is subject to bending moments due both to .centrifugal force and to steam or blade vibration force, such moments being a maximum at the junction of a projection and a blade and a minimum midway between While the moment due to steam or blade vibration force is zero midway between the blades, that due to centrifugal force, for a uniform lashing section, would be one-half of the maximum. By tapering the projections, the lashing is strengthened according to the need, the bending moment midway between blades being reduced to less than one-half of the maximum existing at the blade and projection junction. By providing projections which terminate midway between blades, the joints are located where the bending moments are least, thereby restricting any reduction of physical or mechanical properties made necessary by operations in blade assembly, to locations approximately midway between blades. To enable the projections to be forged, not only must the necessary draft be provided, but heed must be given to the parting line of the forging dies. Therefore, thev projections are properly related to the blades with respect to theA die parting line and are tapered to give the necessary draft, tapering for this purpose assuring yof the maximum thickness where strength is most required, that is, at the blade and projection junction, and minimum thickness and location of projection joints where the bending moment is the lea'st,. namely, at a section approximately midway between the blades.

The foregoing and other objects are eected by the `inventionl as wil-l be apparent from the following: description and :claims taken in connection with the accompanying drawings, forming a part of thisapplication, in which:

Fig.r 1 is a fragmentary view `of a blade row having the improved lashing:

Fig. y2y is a developed sectional view taken along the line II-II of Fig. 1;

Fig. 3 is a sectional view taken along the line line III-III of Fig. 2i; and

Fig. 4' is a sectional view 'taken along the line IV`IV 0f Fig. 2.

In the? drawing, there is shown a row of forged blades l0I having a lashing comprisinglashing structures, at H, connectingadjacenti blades.

Each lashing structure, at Il., includes projections i2 and lid for-ged integrally with the blades and extending outwardly from they `blade convex and concave faces l5 and I6, respectively, and having their respective outer ends l1 and I8 disposed contiguously and connected by a joint I9, for example, a welded connection, located approximately midway between blades.

The projections I2 and I4 are tapered and connected so as to satisfy strength :considerations and to provide the draft required for forging. The lashing must resist centrifugal force as well as steam or vibration force.

With respect to centrifugal force, the maximum bending moment occurs at the junction of a projection and a blade and the minimum bending moment exists at a section midway between blades. With a lashing structure of uniform section, the bending moment midway between blades would be about one-half the maximum. Tapering of the projections, therefore, gives a thick section where strength is most required and a thin section where the strength requirements are least, tapering having the advantage of lessening the bending moment at the section midway between blades-instead of being one-half of the maximum, it is less than one-half, for example, about one-third.

While the bending moment due to steam and vibration force is also a maximum at the blade projection junction, the bending moment midway between blades is zero.

Therefore, tapering to provide the draft required for forging the lashing projections integrally with the blades also assures of strong lashing constructions.

Where, as shown, the blade section is asymmetrical, or of the reaction type, at the projection locations, the end faces of the projections are slanted generally in the same direction as the blade chord passing through the inlet and outlet edges of the section, not only to avoid an excessive side dimension, or an excessive side dimension differential of a, projection from the blade surface t its end face, to make forging easier, but the stress area of bonding material of the joint is thereby increased and the joint better satisfies an average condition of blade connections over the minimum stress zone. In this connection, in Fig. 2, it will be noted that the slant line a-b of the projection end faces extends generally in the same direction as the chord line a-c, these lines including only a small angle.

Interference with flow of elastic fluid in the blade passage is minimized by having the projections of streamlined section in the direction of flow or blade width. In this connection, the projection end faces are slanted, not only for the reasons already given, but to provide for projection forging to a streamlined section with full peripheral draft, as will be seen from Fig. 4, and with regard to the parting line of the blade forging dies.

While the invention has been shown in but one form, it Will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What is claimed is:

1. In combination, a plurality of forged blades of a moving row and lashing means for connecting the blades; said lashing means comprising lashing structures connecting adjacent blades, each lashing structure including projections which are forged integrally -with the blades as the latter are forged and extending from convex and concave blade faces so that their outer ends adjoin approximately midway between the blades and a joint for connecting the adjacent projection ends, said projections tapering from the blade faces to the joint.

2. In combination, a plurality of forged blades of a moving row and lashing means for connecting the blades; said lashing means comprising lashing structures connecting adjacent blades. each lashing structure including projections which are forged integrally with the blades as the latter are forged and extending from convex and concave blade faces so that theii` outer ends adjoin approximately midway between the blades and the outer projection ends being slanted, relative to the plane of blade rotation, generally in the same direction as the slant, relative to said plane, of the blade chord passing through the inlet and outlet blade edges at the projection blade section and a weld joint for connecting the slanted projection ends, said projections tapering from the blade faces to the joint.

3. In combination, a plurality of forged blades of a moving row and lashing means for connecting the blades; said lashing means comprising lashing structures connecting adjacent blades, each lashing structure including projections which are forged integrally with the blades as the latter are forged and extending from convex and concave blade faces so that their outer ends adjoin approximately midway between the blades and the outer projection ends being slanted, relative to the plane of blade rotation, in the same direction as the slant, relative to such plane, of the blade chord passing through the inlet and outlet blade edges at the projection blade section and a weld joint for connecting the slanted projection ends, said projections tapering from the blade faces to the joint and being of streamlined section in the direction of blade width.

JOSEPH D. CONRAD. WILLIAM H. LLOYD.

REFERENCES CITED The following references are of record in the fue of this patent:

UNITED STATES PATENTS Number Name Date 1,618,274 Davis Feb. 22, 1927 1,618,296 Ray Feb. 22, 1927 

